Generic client.Get for custom Kubernetes GO operator - go

Question

In a custom Kubernetes operator implemented with the operator-sdk in golang is it possible to call the custom API directly and retrieve the object as YAML?
For example. I have a custom resource
apiVersion: test.com/v1alpha1
kind: TEST
metadata::
name: example-test
spec:
replicas: 3
randomname: value
I don't know ahead of time what the fields in the spec are going to be apart from replicas. So I am not able to create a go type that includes structs to hold the entries.
So rather than doing:
instance := &testv1alpha1.Test{}
err := r.client.Get(context.TODO(), nameSpaceName, instance)
I want to be able to do something like:
instanceYAML := genericContainer{}
err := r.client.GetGeneric(context.TODO(), nameSpaceName, instance)
and then parse the instanceYAML to check the entries.

Answer 1

This is called the "unstructured" client. The docs are pretty light so I recommend looking over the tests as examples https://github.com/kubernetes-sigs/controller-runtime/blob/ea32729106c995d9df310ac4731c2061490addfb/pkg/client/client_test.go#L1536-L1566

Answer 2

Using the unstructured type client all the operation done on the CoreAPI resource can be done on the CustomResourceDefinition(CRD)
package util
import (
"context"
"encoding/json"
"strconv"
"github.com/go-logr/logr"
"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
"k8s.io/apimachinery/pkg/runtime/schema"
types "k8s.io/apimachinery/pkg/types"
_ "k8s.io/client-go/plugin/pkg/client/auth"
"sigs.k8s.io/controller-runtime/pkg/client"
)
var reqLogger logr.Logger
func CRUDonCRD(c client.Client) {
u := createUnstructuredObject(c)
GetCR(u, c)
PatchCR(u, c, 1)
DeleteCR(u, c)
}
func createUnstructuredObject(c client.Client) *unstructured.Unstructured {
u := &unstructured.Unstructured{}
u.SetGroupVersionKind(schema.GroupVersionKind{
// Group: "<crd group name>",
// Kind: "<crd kind>",
// Version: "<crd version>",
Group: "com.cumulus.netq.operator.transport",
Kind: "TransportOperator",
Version: "v1",
})
_ = c.Get(context.Background(), client.ObjectKey{
// Namespace: "<namespace>",
// Name: "cr name",
Namespace: "default",
Name: "transport-operator",
}, u)
return u
}
type patchStringValue struct {
Op string `json:"op"`
Path string `json:"path"`
Value string `json:"value"`
}
func PatchCR(u *unstructured.Unstructured, c client.Client, replicaCount int) error {
payload := []patchStringValue{{
Op: "replace",
Path: "/spec/replicas/replicasOpta",
Value: strconv.Itoa(replicaCount),
}}
payloadBytes, _ := json.Marshal(payload)
err := c.Patch(context.Background(), u, client.RawPatch(types.JSONPatchType, payloadBytes))
if err != nil {
reqLogger.Error(err, "error occured while patching")
}
reqLogger.Info("Patching is successful", "Patched Transport Operator Object", u)
return err
}
func GetCR(u *unstructured.Unstructured, c client.Client) {
// key := client.ObjectKey{Namespace: "default", Name: "<cr-name>"}
key := client.ObjectKey{Namespace: "default", Name: "transport-operator"}
err := c.Get(context.Background(), key, u)
if err != nil {
reqLogger.Error(err, "error occured while getting the resource")
}
reqLogger.Info("Got the resource", "Resource Object", u)
}
func DeleteCR(u *unstructured.Unstructured, c client.Client) {
err := c.Delete(context.Background(), u)
if err != nil {
reqLogger.Error(err, "error occured while deleting the resource")
}
reqLogger.Info("Resource deleted", "Resource ", u)
}

Answer 3

Here is what I did in the Operator SDK to get a object from kubernetes.
Ref: https://github.com/kubernetes-sigs/controller-runtime/blob/master/pkg/client/example_test.go#L57
func (r *ConfigDeploymentReconciler) findObjectsForConfigMap(configMap client.Object) []reconcile.Request {
pod := &corev1.Pod{}
_ = r.Client.Get(context.Background(), client.ObjectKey{
Namespace: "prometheus",
Name: "prometheus-node-exporter-7vxqs",
}, pod)
fmt.Println("Got this pod", pod.String())
return nil
}